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EpiPens and generic versions may be hard to get in some parts of the U.S., the Food And Drug Administration said Wednesday.

Mylan’s EpiPen, the generic version of the same allergic reaction medicine, and a different brand called Adrenaclick were all having supply and distribution issues, according to the FDA.

This means some families might not be able to get their usual brand when they go to the pharmacy.

So what should people do if they rely on the potentially life-saving injector, which can save someone in the throes of anaphylactic shock after a bee sting or eating a food they’re allergic to?

“They need to be careful. If they run out, they can’t just run to the pharmacy and get a new one,” advised Dr. James Baker, a professor emeritus at the University of Michigan and CEO of Food Allergy Research & Education (FARE).

Check your supply of epinephrine autoinjectors

Check the expiration dates

If you do get an unfamiliar new brand, make sure you know how to use it

"So right now the only autoinjector that appears to be widely available is the Auvi-Q,” Baker said.

What's most important is for patients to understand how to use a different brand from the one they are used to, the American Academy of Allergy, Asthma and Immunology says.

Auvi-Q, an auto-injectable epinephrine device, used to treat anaphylaxis due to allergies and also featuring voice instructions through a small speaker. The maker of Auvi-Q says it is available across the country. Chase Stevens / Las Vegas Review-Journal via AP

"If you have a severe allergy and carry epinephrine, it is important to know that each brand functions a little differently. The stress of an anaphylactic reaction is not the time to realize you have a different autoinjector than what was demonstrated to you by your allergist," the group, which represents allergy experts, says on its website.

While the medication is the same, the method for injecting it is different for each brand.

"The next time you pick up your prescription, be sure to compare the brand and dose you received with the brand you have been trained to use. If the medication appears to be different than what you expected, find out why a substitution was made. Also, be sure to get a demonstration on how to use the product."